Can you fetch a basic land with Evolving Wilds during your opponent's end step?

Evolving Wilds reads: '{T}, Sacrifice Evolving Wilds: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.' This is an activated ability with no timing restriction printed on it, meaning it follows the rules for activated abilities in general.

Under CR 116.1a and CR 602.1, activated abilities without a 'Sorcery speed' or 'activate only as a sorcery' restriction can be activated any time you have priority — during any player's turn, including during your opponent's end step (which is still a main phase or a step where you can receive priority after something resolves or the active player passes).

The end step is a regular step in which both players receive priority (CR 500.1, CR 116.3). As long as the stack is empty and your opponent passes priority, you will receive priority and may activate Evolving Wilds at that point. The fetched land enters tapped, so it won't produce mana that turn, but it will be available untapped on your next turn.

Concrete example: It is your opponent's end step. They pass priority. You activate Evolving Wilds, sacrificing it to search for a Forest, which enters the battlefield tapped. That Forest will untap during your next untap step, ready to produce mana on your turn.

This is a common strategic play — fetching at end of turn shuffles your library after any scry manipulation and ensures the land is ready for your upcoming turn without giving your opponent extra information about your plans during your own turn.