Montclair said it had hoped to reach a negotiated deal, but the Equal board turned down the offer of $4 per share in cash on March 15.
"While our goal is to reach a negotiated transaction with Equal Energy, we have determined that Equal Energy shareholders should be informed of our interest in an acquisition such that they can consider for themselves whether our proposal should be pursued by the company," Montclair chief executive Cobb Hazelrig said in a statement.
Montclair said it will now evaluate all of its options including the possibility of nominating a slate of independent directors to Equal Energy's board and more talks with the company's management.
Montclair noted it was not currently soliciting proxies or consents from Equal Energy shareholders.
Equal Energy holds a portfolio of oil and gas properties in Oklahoma.
Shares in the company closed up 31 cents or nearly nine per cent at $3.92 on the Toronto Stock Exchange on Monday.