English:
In English, a consistent order has been found for the acquisition of the grammatical morphemes (eg -ing, plural -s, possessive -s, etc) among child and adult learners of English with different L1s (Dulay and Burt, 1973, 1974, and Bailey, Madden and Krashen, 1974, reviewed in Ellis, R, 1994: 91). For example, the morphemes -ing, plural -s and the -s which marks the copular verb (It's good) are acquired well before morphemes such as the past tense marker -ed, the 3rd person singular present -s (He works) and the possessive -s (The dog's bone). Similarly, the grammar of questions in English is acquired in predictable stages. For more on stages of acquisition in English, see Lightbown and Spada, 1999: chapter 4.

German:
German word order seems to develop in predictable stages (Pienemann, Johnston and Brindley, 1988, reviewed in Ellis, R, 1994: 103). At Stage 1, learners use only a single, 'canonical' word order (usually SVO: subject - verb - object). At Stage 2, adverbs start to be moved to the front of the clause, but learners show no sign of inverting the subject and verb, normally required by the fronted adverb (the so-called Verb-second rule). At Stage 3, learners are able to move non-finite verb forms to the end of the clause, while changes to the canonical SVO order finally appear at Stage 4, as learners master inversion of subject and verb after adverbials (the Verb-second rule). Finally, a further change to the canoncial SVO order is mastered, with finite verbs being correctly placed at the end of subordinate clauses.

French:
Further evidence that variation from a basic word order is initially avoided by learners comes from Devitt's (1993) study of children acquiring L2 French in France. In French, the basic word order is SVO. However, object pronouns (eg te, lui, le, la) are placed before the verb. Devitt's learners simplified their task by initially placing the object pronoun after the verb. It then took them a while to differentiate the different forms of personal pronouns: stressed pronouns (toi, lui, elle) are acquired before unstressed (te, le, la), and direct pronouns (le, la, les) before indirect (lui, leur).

Devitt (1993) also found stages of development for French verb morphology. Consistent with our picture of early interlanguage, his subjects started out with very little morphology. Two verb forms dominated early interlanguage: a form corresponding to the present tense stem, eg achète and a form ending in the sound /e/ (written as é), eg acheté). Gradually, this é-form came to be used for past events with the other form being used for present descriptions and actions, and past descriptions. Two imperfect forms j'avais (I had) and j'étais (I was) then appeared, but with no evidence of any other imperfect tense conjugations. The children then integrated auxiliary verbs to form the compound perfect tense and began to differentiate between the two auxiliaries required for this. By Stage 4, odd pluperfect and imperfect forms were starting to appear. This development of tense marking seems to be reflected in more recent studies with instructed adult learners (see Howard, 2002).