Magnolia Oil & Gas Corporation
US ˙ NYSE ˙ US5596631094

SecurityMGY / Magnolia Oil & Gas Corporation
InstitutionSei Investments Co
Latest Disclosed Ownership235,749 shares
Latest Disclosed Value $ 5,160,425
Sei Investments Co reports 23.59% increase in ownership of MGY / Magnolia Oil & Gas Corporation

On February 13, 2026 - Sei Investments Co filed a 13F-HR form disclosing ownership of 235,749 shares of Magnolia Oil & Gas Corporation (US:MGY) valued at $5,160,546 USD as of December 31, 2025. The entity filed a previous 13F-HR on November 13, 2025 disclosing 190,750 shares of Magnolia Oil & Gas Corporation. This represents a change in shares of 23.59% during the quarter. The current value of the position is $6,485,455 USD.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

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Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date		 Effective
Date		Form Security Class ID Avg Price
Paid (Est)		 Reported
Shares		 ΔShares ΔShares
(%)		 Reported
Value
(x1000)		 ΔValue
(%)		 Alloc
(%)		 ΔAlloc ΔAlloc (%) Cost Basis
(x1000)		 Unrealized
Gain/Loss
(x1000)
2026-02-13 2025-12-31 13F MAGNOLIA OIL & GAS CL A 559663109 235,749 44,999 23.59 5,160 13.36 0.0051
2025-11-13 2025-09-30 13F MAGNOLIA OIL & GAS CL A 559663109 190,750 11,838 6.62 4,553 13.21 0.0049
2025-08-14 2025-06-30 13F MAGNOLIA OIL & GAS CL A 559663109 178,912 -616,561 -77.51 4,022 -79.99 0.0047
2025-05-14 2025-03-31 13F/A-1 MAGNOLIA OIL & GAS CL A 559663109 795,473 -5,033 -0.63 20,094 7.36 0.0259
2025-05-13 2025-03-31 13F MAGNOLIA OIL & GAS CL A 559663109 800,350 -156 18,721 0.0204
2025-02-11 2024-12-31 13F MAGNOLIA OIL & GAS CL A 559663109 800,506 -56,654 -6.61 18,716 -10.59 0.0240
2024-11-12 2024-09-30 13F MAGNOLIA OIL & GAS CL A 559663109 857,160 44,378 5.46 20,932 1.63 0.0272
2024-08-13 2024-06-30 13F MAGNOLIA OIL & GAS CL A 559663109 812,782 77,934 10.61 20,596 8.00 0.0292
2024-05-07 2024-03-31 13F MAGNOLIA OIL & GAS CL A 559663109 734,848 -120,778 -14.12 19,069 4.68 0.0279
2024-02-14 2023-12-31 13F MAGNOLIA OIL & GAS CL A 559663109 855,626 37,229 4.55 18,216 -2.84 0.0292
2023-11-14 2023-09-30 13F MAGNOLIA OIL & GAS CL A 559663109 818,397 47,564 6.17 18,750 16.38 0.0337
2023-08-11 2023-06-30 13F MAGNOLIA OIL & GAS CL A 559663109 770,833 117,388 17.96 16,110 12.68 0.0281
2023-05-12 2023-03-31 13F MAGNOLIA OIL & GAS CL A 559663109 653,445 148,045 29.29 14,297 20.64 0.0266
2023-02-10 2022-12-31 13F MAGNOLIA OIL & GAS CL A 559663109 505,400 33,318 7.06 11,852 26.72 0.0263
2022-11-14 2022-09-30 13F MAGNOLIA OIL & GAS CL A 559663109 472,082 -29,669 -5.91 9,352 -11.23 0.0209
2022-08-15 2022-06-30 13F MAGNOLIA OIL & GAS CL A 559663109 501,751 107,429 27.24 10,535 12.96 0.0228
2022-05-13 2022-03-31 13F MAGNOLIA OIL & GAS CL A 559663109 394,322 11,759 3.07 9,326 29.20 0.0187
2022-02-14 2021-12-31 13F MAGNOLIA OIL & GAS CL A 559663109 382,563 163,098 74.32 7,218 85.03 0.0135
2021-11-12 2021-09-30 13F MAGNOLIA OIL & GAS CL A 559663109 219,465 -102,581 -31.85 3,901 -22.51 0.0082
2021-08-06 2021-06-30 13F MAGNOLIA OIL & GAS CL A 559663109 322,046 114,303 55.02 5,034 111.07 0.0112
2021-05-12 2021-03-31 13F MAGNOLIA OIL & GAS CL A 559663109 207,743 -1,266 -0.61 2,385 61.59 0.0060
2021-02-08 2020-12-31 13F MAGNOLIA OIL & GAS CL A 559663109 209,009 -189,576 -47.56 1,476 -28.35 0.0038
2020-12-04 2020-09-30 13F/A-1 MAGNOLIA OIL & GAS CL A 559663109 398,585 135,812 51.68 2,060 29.32 0.0060
2020-11-06 2020-09-30 13F MAGNOLIA OIL & GAS CL A 559663109 398,585 135,812 2,060 4,960.0220
2020-08-17 2020-06-30 13F/A-1 MAGNOLIA OIL & GAS CL A 559663109 262,773 -17,476 -6.24 1,593 42.11 0.0049
2020-08-11 2020-06-30 13F MAGNOLIA OIL & GAS CL A 559663109 316,366 36,117 3,830 10,389.0789
2020-05-14 2020-03-31 13F MAGNOLIA OIL & GAS CL A 559663109 280,249 -13,098 -4.47 1,121 -69.62 0.0041
2020-02-06 2019-12-31 13F MAGNOLIA OIL & GAS CL A 559663109 293,347 32,110 12.29 3,690 27.24 0.0110
2019-11-12 2019-09-30 13F MAGNOLIA OIL & GAS CL A 559663109 261,237 50,136 23.75 2,900 18.61 0.0074
2019-08-14 2019-06-30 13F MAGNOLIA OIL & GAS CL A 559663109 211,101 68,880 48.43 2,445 43.23 0.0080
2019-05-15 2019-03-31 13F MAGNOLIA OIL & GAS CL A 559663109 142,221 142,221 1,707 0.0057
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.