Commodore International Ltd. yesterday reported a net loss of $53.2 million for the fourth quarter of 1985, despite posting sales that were the second highest in the computer company's history.

Restructuring charges of $22 million from the closing of assembly operations in Corby, England, and a semiconductor plant in Costa Mesa, Calif., and adjustments of $29 million against other assets contributed to the loss, Commodore said in a statement.

"While these actions had a significant adverse effect on reported results, during the December quarter, Commodore generated strong cash flow and repaid $51.5 million of its debt," Chairman Irving Gould said.

Commodore, which is based in West Chester, Pa., is in technical default on provisions of its loan agreements. Gould said the company is working closely with its major banking partners and expects to reach a satisfactory new lending agreement in the near future.

Commodore's loss of $53.2 million in the last three months of 1985 compared with net income of $3.2 million (10 cents a share) in the same period a year earlier. Gould said Commodore earned a pretax profit of $1.05 million before the write-offs and write-downs.

Commodore's net sales in the quarter, the second of its fiscal year, were $339.2 million, up less than 1 percent from the same period of 1984 and more than twice the $159.2 million recorded in the three months ending last Sept. 30.

For the first six months of its fiscal year, Commodore had a net loss of $92.4 million compared with net income of $30.9 million ($1.00) in the same period a year earlier. Six-month sales were $498.4 million, down 14 percent from $582.9 million a year earlier.

The most sales the company ever recorded in one quarter was $431.4 million in the three months that ended Dec. 31, 1983.

*Occidental Petroleum Corp. yesterday said net earnings were off by 71 percent in the fourth quarter but up by 22 percent for the year. Most of the changes were attributed to gains from the sale of assets.

Occidental showed income of $52.7 million (27 cents a share) on sales of $3.78 billion for the fourth quarter compared with a year earlier, when it earned $184.2 million ($1.16) on sales of $4 billion.

For all of 1985, the company earned $696 million ($4.49) on sales of $14.53 billion compared with 1984 when it earned $568.7 million ($3.05) on revenue of $15.59 billion.

Occidental said its earnings last year included gains of $479.2 million on the sale of foreign and domestic oil and gas operations, including half of its Colombian holdings and 25 percent of its holdings in Libya.

Of that amount, $22.8 million occurred in the fourth quarter.

*Schlumberger Ltd., a New York-based oilfield services company, reported a quarterly loss of $372.6 million, versus a gain of $311.1 million a year earlier. Without $486 million in fourth-quarter charges relating to its Fairchild Semiconductor group, however, the company would have earned $113 million (38 cents), it said.

Schlumberger said its 1985 net income was $351 million ($1.17), versus $1.18 billion ($4.10) in 1984. Without total nonrecurring charges of $511 million relating to Fairchild Semiconductor, it said its net income would have been $862 million, down 27 percent, with per-share earnings of $2.88.

Those charges included the write-off of the balance of goodwill of $250 million, a provision of $106 million for disposal of assets and $81 million for consolidation of production facilities, the company said. Goodwill represents intangible assets, including such things as a company's reputation and its relations with customers.

Schlumberger's quarterly revenue was down 2 percent to $1.67 billion from $1.70 billion a year earlier. The company's total 1985 revenue increased 3 percent to $6.56 billion from $6.37 billion.